Expression, characterization and antibacterial effects of two endolysins as novel biocontrol agents against Pseudomonas oleovorans in foods.

Abstract

Endolysins encoded by bacteriophages have been reported to be the novel antibacterial agents for foodborne pathogens. However, there remains a research gap in identifying endolysins with broad lytic spectra and high activity for applications in food industry. To address this gap, the present study aimed to express, purify, and biochemically characterize two endolysins, LysPS3-1 (Peptidase M15-like superfamily) and LysPS5 (Muraidase), derived from Salmonella phage PS3-1 and polyvalent phage PS5, respectively. LysPS3-1 and LysPS5 were found to have wide lytic spectra, and strong lytic activities against chloroform-treated V. vulnificus, S. typhimurium, P. oleovorans and E. coli O157. After incubation at -20-60 °C, at pH 3.0-12.0, and in the presence of NaCl at 25-1000 mM for 1 h, both endolysins still exhibited high lytic activities (≥80%). In addition, LysPS3-1 or LysPS5 (5 μg/mL) combined with EDTA (0.1-5 mM) showed effective synergistic antibacterial and bactericidal effect against P. oleovorans. After treatment with 0.5 mM EDTA and 100 μg/mL LysPS3-1 or LysPS5 for 3 h in LB broth, the viable P. oleovorans counts were significantly reduced (P < 0.05). This combination also significantly reduced the viable counts of P. oleovorans in liquid (milk and juice) and solid (bacon and salmon) foods at 4 °C (P < 0.05). Therefore, these two endolysins could be used as potential antibacterial agents for controlling food spoilage bacteria in food industry.